Amyloidosis can be primary or secondary to other diseases including tuberculosis, syphilis, chronic renal disease, hypergammaglobulinemia, rheumatoid arthritis, malignancies, and multiple myeloma.[1
] Secondary amyloidosis seldom involves the lungs, but primary systemic amyloidosis frequently involves multiple systems including the heart, gastrointestinal tract, kidneys, and skin.[1
] Primary amyloidosis with involvement of only 1 system (localized amyloidosis) is uncommon, and disease with only respiratory system involvement alone is rare.[7
] In patients with primary respiratory amyloidosis, amyloid is deposited in the pulmonary parenchyma and submucosa of the bronchi and trachea, pleura and lymph nodes in the mediastinum, and hilum of lungs.[11
] Utz et al
] retrospectively analyzed the clinical record of patients seen at the Mayo Clinic over a 13-year period (1980–1993), and of 55 patients with pathologically proven amyloidosis only 11 had the disease confined to the respiratory system.
Primary pulmonary amyloidosis is classified into 4 types according to the site of the lesions[7
] : tracheobronchial amyloidosis; nodular amyloidosis; infiltrating interstitial amyloidosis, and lymph node amyloidosis. Tracheobronchial amyloidosis is the most frequently seen in clinical practice, and the clinical manifestations included dyspnea, chest tightness, cough, expectoration, and hemoptysis.[7
] Chest radiographs and CT show increased lung markings, obstructive pneumonia and atelectasis, localized or diffuse stenosis of the trachea, thickened trachea and bronchus and nodular shadows in the lumen with occasional calcifications. Bronchoscopy shows single or multiple protrusions or generalized thickening of the bronchial wall and bronchial stenosis. The smooth protrusions have no nodules, are of different sizes, and are susceptible to bleeding on touch. Occasionally, the protrusions may obstruct the bronchus resulting in secondary infection. In some cases, the whole submucosa of the bronchus is infiltrated with amyloid substance leading to bronchial stenosis. In the present study, 7 patients developed tracheobronchial stenosis (53.8%) and their clinical manifestations were similar to previously reported.
Patients with nodular amyloidosis usually have a cough or hemoptysis, and imaging findings show single or multiple nodules or patchy shadows, and involvement of other organs is seldom found.[12
] In the present study, 3 patients had nodular amyloidosis, 2 of whom received surgical resection of solitary nodular lesions.
Infiltrating interstitial amyloidosis is characterized by massive deposition of amyloid substances in small blood vessels and the pulmonary interstitium.[13
] High resolution CT shows thickening of interlobular septum, network-like blurred shadows, or multiple subpleural nodules (2–4 mm in size). Lymph node amyloidosis is characterized by deposition of amyloid substances in lymph nodes in the mediastinum and pulmonary hilum.[14
] The condition is rarely seen in patients without systemic amyloidosis, and was found in only 2 patient in the present study.
Pathological examination of a tissue specimen is the gold standard for the diagnosis of amyloidosis. Under a light microscope, hematoxylin & eosin (H&E) staining shows homogeneous, pink amyloid substances without cellular structure that are usually accompanied by fibrosis, and characteristic red-green birefringence is seen under polarizing microscopy in Congo red-stained tissue.[2
] The edge of cord or mass-like amyloid substances were blur and their outlines become light gradually.
The principles in the treatment of amyloidosis are to inhibit the synthesis of amyloid and its extracellular deposition, reduce the production of amyloid precursors, and promote the degradation of amyloid.[1
] To date, there are no completely effective therapies and the effectiveness of glucocorticoid, vitamin E, colchicine, and other drugs is not clear.[11
] Resection of intratracheal and bronchial lesions with Nd-YAG laser or endoscopic clipping has been reported.[10
] External beam radiation therapy has also been attempted with promising results, in spite of the underlying mechanisms.[15
] Systemic chemotherapy consisting of 0.15 mg/ kg/d melphalan plus 20 mg/d prednisone for 4 weeks (MP regime) is one of the most commonly used treatments and is believed to inhibit the production and deposition of amyloid.[8
] In the present study, only 1 patients were treated with the MP regimen with good results. Kyle et al
] treated patients with primary systemic amyloidosis with colchicine (n
= 72), MP regimen (n
= 77), or MP regimen in combination with colchicine (n
= 71) and reported median survival times of 8.5 months, 18 months, and 17 months, respectively.
The primary limitation of this study is its retrospective nature. However, amyloidosis involving only the respiratory system is very rare and this report is of a relatively large number of patients.